The field of the invention relates to chimney constructions for prefabricated fireplaces and the like.
There are a number of chimney constructions which are available for use with factory built fireplaces. U.S. Pat. Nos. 4,082,322, 4,236,498, 4,259,941, 4,271,815, 4,466,340 and 4,700,687 disclose a number of such fireplaces and chimney constructions associated therewith. Generally speaking, two of the more popular types of chimney constructions can be described as two wall and three wall systems.
Two wall chimney constructions are generally less expensive taen three wall constructions. They include two concentric pipes which are mounted to the fireplace and extend through the roof of the building. The inner pipe functions as a flue pipe and is made from stainless steel or other heat-resistant material. The outer pipe is made from steel and may have a galvanized outer surface. Such systems operate by pulling in cooling air from the base of the chimney through a turnaround assembly. The area surrounding the fireplace is referred to as the enclosure cavity. The cooling air flows upwardly between the two pipes when the fireplace is in use, thereby continuously removing heat. The "turnaround assembly" defined by an outer collar, is provided at the top of the fireplace to allow such an air flow. In contrast, three wall systems include three concentric pipes and operate by means of thermal siphoning. Cooling air is taken from the outside rather than the enclosure cavity and is drawn down between the outer and middle pipes. The air is expelled up and out from between the middle and flue pipes by natural convection.